1. Technical Field
The present invention relates to a communication apparatus capable of transceiving a packet including encrypted data, a reception control method, and a transmission control method.
2. Background Art
In general, to prevent data leakage in packet communication, a transmitting side encrypts and transmits data included in a packet, and a receiving side decrypts encrypted data of the packet received therein. An IP sec (Security Architecture for Internet Protocol) is used as an encryption protocol for packet communication over the Internet. Recently, a lookaside-type communication apparatus is generally used as a communication apparatus employing the IP sec. As shown in FIG. 1, the lookaside-type communication apparatus has a structure in which a transmission and reception part 1 and a security part 2 are connected to a control part 3 through a system bus 4. The conventional device having the above structure is disclosed in patent literature 1 and patent literature 2.
The transmission and reception part 1 transmits and receives packets to and from a network 5, and the security part 2 encrypts data to be transmitted and decrypts encrypted data that have been received. The control part 3 controls the transmission and reception part 1 and the security part 2. When data are encrypted and transmitted in packet transmission, the control part 3 supplies the data to be transmitted to the security part 2 through the system bus 4, and the security part 2 encrypts the supplied data and returns the encrypted data to the control part 3 through the system bus 4. Thereafter, the control part 3 supplies transmit data including the encrypted data and a header to the transmission and reception part 1 through the system bus 4, and the transmission and reception part 1 makes the supplied transmit data in the form of a packet and transmits the packet toward an address of a destination within the network 5. When receive data are decrypted in packet reception, the receive data included in a packet received by the transmission and reception part 1 are supplied to the control part 3 through the system bus 4. If the receive data contains encrypted data, the control part 3 supplies the encrypted data to the security part 2 through the system bus 4. The security part 2 decrypts the encrypted data that have been supplied thereto, and returns the decrypted data, that is, plain-text data to the control part 3 through the system bus 4.